Electrophoretic dispersion, electrophoretic display device, method of manufacturing electrophoretic display device, and electronic system

ABSTRACT

To provide an electrophoretic dispersion capable of reducing or preventing the aggregation of electrophoretic particles, an electrophoretic display device using the electrophoretic dispersion, a method of manufacturing the electrophoretic display device, and an electronic system superior in display performance; an electrophoretic display device (electrophoretic display unit) has: a first substrate with a first electrode; a second substrate with a second electrode opposite the first electrode; and an electrophoretic dispersion provided between the first substrate and second substrate. The electrophoretic dispersion (dispersion for electrophoretic display units) includes a liquid phase insulative dispersion medium and electrophoretic particles dispersed in the dispersion medium, the particles electrophoretically migrated under an influence of an electric field. Also included as the electrophoretic particles, inorganic particles and resin particles dyed a color different from that of the inorganic particles and having an electrical polarity opposite to that of the inorganic particles.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an electrophoretic dispersion, anelectrophoretic display device, a method of manufacturing anelectrophoretic display device, and an electronic system.

2. Description of Related Art

In recent years, portable information systems have been intensivelyenhanced. Demand for thin display devices with low power consumption areparticularly growing. Various attempts have been made to cope with suchdemands. Liquid crystal display devices (liquid crystal display units)have satisfied the demands until now.

SUMMARY OF THE INVENTION

However, such liquid crystal display devices have a problem in thatdisplay visibility is reduced depending on the view angle or due toreflected light. Also, a viewer's eyes may suffer from the flicker oflight sources. Therefore, numerous attempts are being made to developdisplay devices harmless to eyes.

Reflective display devices are attracting much attention because theunits have low power consumption and are harmless to eyes. Anelectrophoretic display device (electrophoretic display unit) is knownas one of the reflective display devices.

FIG. 15 illustrates the operational principle of a related artelectrophoretic display device. The electrophoretic display device 920includes: charged electrophoretic particles 905; a colored insulatingliquid (dispersion medium) 906 containing a dissolved colorant; and apair of substrates 901 having the respective transparent electrodes 903facing each other with the colored insulating liquid 906 placedtherebetween.

When a voltage is applied to the colored insulating liquid 906 throughthe transparent electrodes 903, the charged electrophoretic particles905 are attracted toward the transparent electrode 903 having anelectrical polarity opposite to that of the charged particles 905.

In the electrophoretic display device 920, the display is provided basedon the contrast in color between the charged electrophoretic particles905 and the colored insulating liquid 906. In addition, desiredinformation (picture image) can be displayed by forcing the transparentelectrodes 903 arranged on one side to form a desired pattern.

Specifically, when a voltage is applied to the transparent electrodes903 to provide the electrodes with a given polarity and to cause thewhite electrophoretic particles 905 to be attracted toward thetransparent electrodes 903 placed close to observers, the observers canobserve the information through the desired pattern in white using thecolor of the colored insulating liquid 906 as its background. Further,when a voltage is applied to the transparent electrodes 903 so that thereversed situation arises, the electrophoretic particles 905 areattracted toward the electrode on the opposite side and the observersobserve the color of the colored insulating liquid 906.

The principle of a related art electrophoretic display device 920 is asdescribed above. But the electrophoretic display device 920 illustratedin FIG. 15 has a problem such that the display contrast is low becausespaces between the electrophoretic particles 905 are filled with thecolored insulating liquid 906 in a display state in white.

In order to cope with the problem, electrophoretic display devices havebeen proposed, which use two types of electrophoretic particles havingelectrical polarities opposite to each other and different colors (colortones) and use an insulating liquid which is colorless and transparent.

However, the related art electrophoretic display device has thefollowing problems of unreliable dispersion of electrophoretic particlesin the insulating liquid because of using pigment particles havingdifferent sizes as the electrophoretic particles, the difficulty inperforming the crushing of the electrophoretic particles, etc.

The related art electrophoretic display device has a problem such thatit is difficult for the electrophoretic particles to electrophoreticallymigrate in the insulating liquid because a surfactant is used in orderto enhance the dispersibility and electrification of the electrophoreticparticles. Thus the electrophoretic particles are aggregated due to thesurfactant adhering to the particles.

In order to cope with the aggregation of the two types of particles, atechnique to process the surface of one type of particles with acoupling agent is disclosed.

However, the related art method has a problem such that the satisfyinganti-aggregation effect cannot be obtained depending on the constitutivematerials and combination of the two types of particles.

The invention provides an electrophoretic dispersion that reduces orprevents the aggregation among electrophoretic particles, anelectrophoretic display device using the electrophoretic dispersion, amethod of manufacturing the electrophoretic display device, and anelectronic system superior in display performance.

The electrophoretic dispersion of an aspect of the invention is anelectrophoretic dispersion including: an insulative liquid phasedispersion medium; and electrophoretic particles dispersed in theinsulative dispersion medium and electrophoretically migrated under aninfluence of an electric field, the electrophoretic particles includinginorganic particles, and resin particles dyed a color different fromthat of the inorganic particles and having an electrical polarityopposite to that of the inorganic particles.

Thus, the aggregation of the electrophoretic particles (the aggregationof the inorganic particles and resin particles) can be reduced orprevented.

In the electrophoretic dispersion of an aspect of the invention, theresin particles may be made mainly from an acrylic resin.

Thus, the aggregation of the electrophoretic particles can be reduced orprevented.

In the electrophoretic dispersion of an aspect of the invention, theacrylic resin may have, as a polar group, at least one of a hydroxylgroup and an amino group.

Thus, the resistance property of the resin particles with respect to theliquid phase dispersion medium can be increased.

In the electrophoretic dispersion of an aspect of the invention, thepolar group may be introduced by copolymerizing an acrylic monomerhaving the polar group with the acrylic resin.

According to such a method, it is possible to obtain an acrylic resinhaving a polar group relatively readily at a high yield.

In the electrophoretic dispersion of an aspect of the invention, theresin particles may be dyed any one of red, green, blue, and black.

Thus, it becomes possible to display information in multiple colors.

In the electrophoretic dispersion of an aspect of the invention, arelation such that B/A falls in 1.5-200 may be satisfied, where theinorganic particles have an average particle size of A[μm] and the resinparticles have an average particle size of B[μm].

Thus, it becomes possible to effectively reduce or prevent theaggregation of the inorganic particles and resin particles whilemaintaining the dispersibilities of the inorganic particles and resinparticles in the liquid phase dispersion medium suitably.

In the electrophoretic dispersion of an aspect of the invention, theaverage particle size of the resin particles may be 0.5-20 μm.

This can achieve the effects of effectively reducing or preventing theaggregation of the inorganic particles and resin particles whilemaintaining the dispersibilities of the inorganic particles and resinparticles in the liquid phase dispersion medium suitably, preventingelectrophoretic display devices from upsizing, preventing the reductionin production efficiency, and the like.

The electrophoretic display device of an aspect of the invention ischaracterized by includes: a first substrate; a second substrateopposite the first substrate; an electrophoretic dispersion locatedbetween the first substrate and the second substrate, theelectrophoretic dispersion including an insulative liquid phasedispersion medium and electrophoretic particles dispersed in theinsulative dispersion medium and electrophoretically migrated under aninfluence of an electric field; a pair of electrodes to cause anelectric field to act on the electrophoretic particles; and theelectrophoretic particles including inorganic particles and resinparticles dyed a color different from that of the inorganic particlesand having an electrical polarity opposite to that of the inorganicparticles.

Thus, an electrophoretic display device superior in display performancecan be obtained.

The electrophoretic display device of an aspect of the inventionincludes: a first substrate; a second substrate opposite the firstsubstrate; microcapsules encapsulating an electrophoretic dispersionlocated between the first substrate and the second substrate, theelectrophoretic dispersion including an insulative liquid phasedispersion medium and electrophoretic particles dispersed in theinsulative dispersion medium and electrophoretically migrated under aninfluence of an electric field; a pair of electrodes for causing anelectric field to act on the electrophoretic particles; and theelectrophoretic particles including inorganic particles, and resinparticles dyed a color different from that of the inorganic particlesand having an electrical polarity opposite to that of the inorganicparticles.

Thus, an electrophoretic display device superior in display performancecan be obtained.

The electrophoretic display device of the invention may have a pluralityof TFT (thin film transistor) elements arranged in a matrix.

Thus, an electrophoretic display device having a high speed of responsecan be obtained.

The electrophoretic display device of an aspect of the invention mayfurther include: a plurality of TFT elements arranged in a matrix; and aplurality of cell spaces partitioned off by partitions and formedbetween the first and second substrates, the cell spaces are each filledwith the electrophoretic dispersion, and each of the cell spacescorresponding to at least one of the TFT elements.

Thus, it becomes possible to display an image in multiple colors bycombining the colors of electrophoretic dispersions filled in the cellspaces.

The electrophoretic display device of an aspect of the invention mayinclude a plurality of TFT elements arranged in a matrix, plural kindsof the microcapsules including the resin particles dyed different colorsprovided between the first and second substrates, and each of themicrocapsules corresponding to at least one of the TFT elements.

Thus, it becomes possible to display an image in multiple colors.

A method of manufacturing the electrophoretic display device of anaspect of the invention is a method of manufacturing an electrophoreticdisplay device including: a first substrate; a second substrate oppositethe first substrate; an electrophoretic dispersion located between thefirst substrate and the second substrate, the electrophoretic dispersionincluding an insulative liquid phase dispersion medium andelectrophoretic particles dispersed in the insulative dispersion mediumand electrophoretically migrated under an influence of an electricfield; a pair of electrodes to cause an electric field to act on theelectrophoretic particles; a plurality of TFT elements arranged in amatrix; the electrophoretic particles including inorganic particles andresin particles dyed a color different from that of the inorganicparticles and having an electrical polarity opposite to that of theinorganic particles; a plurality of cell spaces partitioned off bypartitions and formed between the first and second substrates; the cellspaces each filled with the electrophoretic dispersion; and each of thecell spaces corresponding to at least one of the TFT elements, themethod including filling the cell spaces with the electrophoreticdispersion by a process using a dispenser or by an ink-jet method.

According to such a method, the electrophoretic dispersion can be filledinto the cell spaces more readily and reliably.

A method of manufacturing the electrophoretic display device of anaspect of the invention is a method of manufacturing an electrophoreticdisplay device including: a first substrate; a second substrate oppositethe first substrate; microcapsules encapsulating an electrophoreticdispersion located between the first substrate and the second substrate,the electrophoretic dispersion including an insulative liquid phasedispersion medium and electrophoretic particles dispersed in theinsulative dispersion medium and electrophoretically migrated under aninfluence of an electric field; a pair of electrodes to cause anelectric field to act on the electrophoretic particles; a plurality ofTFT elements arranged in a matrix; the electrophoretic particlesincluding inorganic particles, and resin particles dyed a colordifferent from that of the inorganic particles and having an electricalpolarity opposite to that of the inorganic particles; plural kinds ofmicrocapsules including resin particles dyed different colors providedbetween first and second substrates; and each of the microcapsulescorresponding to at least one of the TFT elements, the methodcharacterized by including fixing a given kind of microcapsules,including resin particles dyed a given color, on the first substrate orthe second substrate through an adhesive so as to electrically connectwith a target TFT element of the TFT elements; and repeating at least anumber of times depending on the kind of microcapsules.

According to such method, the microcapsules can be placed on thesubstrate more readily and reliably.

The electronic system of an aspect of the invention includes theelectrophoretic display device of an aspect of the invention.

Thus, an electronic system superior in display performance can beobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional schematic showing a firstexemplary embodiment of the electrophoretic display device of theinvention;

FIG. 2 is a schematic showing the working principle of theelectrophoretic display device illustrated in FIG. 1;

FIG. 3 is a schematic showing a second exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 4 is a schematic showing a step of a manufacturing process of theelectrophoretic display device illustrated in FIG. 3;

FIG. 5 is a schematic showing a third exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 6 is a schematic showing a fourth exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 7 is a schematic showing a fifth exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 8 is a schematic showing a sixth exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 9 is a schematic showing a seventh exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 10 is a schematic showing an eighth exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 11 is a schematic showing a ninth exemplary embodiment of theelectrophoretic display device of the invention;

FIG. 12 is a longitudinal cross-sectional schematic showing a tenthexemplary embodiment of the electrophoretic display device of theinvention;

FIG. 13 is a schematic showing an exemplary embodiment in the case wherethe electronic system of the invention is applied to an electronicpaper;

FIG. 14 a and 14 b are schematics showing an exemplary embodiment in thecase where the electronic system of the invention is applied to adisplay; and

FIG. 15 is a longitudinal cross-sectional schematic showing theoperational principle of a related art electrophoretic display device.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An electrophoretic dispersion, an electrophoretic display device, amethod of manufacturing the electrophoretic display device, and anelectronic system, according to aspects of the invention will bedescribed in detail below in reference to the accompanying drawings.

First Exemplary Embodiment

A first exemplary embodiment of the electrophoretic display device ofthe invention will be described first.

FIG. 1 is a longitudinal cross-sectional schematic showing the firstexemplary embodiment of the electrophoretic display device of theinvention. FIG. 2 is a schematic showing the working principle of theelectrophoretic display device illustrated in FIG. 1.

For convenience of explanation, in the description to be presentedbelow, the upper sides in the FIGS. 1 and 2 are expressed by “top” or“above” and the lower sides are expressed by “bottom” or “below.”

The electrophoretic display device (electrophoretic display unit) 20illustrated in FIG. 1 has: a first substrate 1 with a first electrode 3;a second substrate 2 with a second electrode 4 facing the firstelectrode 3; and an electrophoretic dispersion 10 provided between thefirst substrate 1 and the second substrate 2. The portions thereof willbe described below in turn.

The first substrate 1 and the second substrate 2 are each composed of asheet (plate) member, and have the functions of supporting andprotecting the members disposed therebetween.

The substrates 1, 2 may be each either flexible or rigid, but it ispreferable that they have flexibility. Use of the flexible substrates 1,2 can offer an electrophoretic display device 20 having flexibility,i.e. an electrophoretic display device 20 useful for, for example,making up an electronic paper.

When the flexible substrates 1, 2 are made, their constitutive materialseach include, for example, a polyolefin, e.g. polyethylene,polypropylene, and ethylene-vinyl acetate copolymer, a modifiedpolyolefin, a polyamide (e.g. Nylon 6, Nylon 46, Nylon 66, Nylon 610,Nylon 612, Nylon 11, Nylon 12, Nylon 6-12, Nylon 6-66), a thermoplasticpolyimide, a liquid crystal polymer, such as aromatic polyester,polyphenylene oxide, polyphenylene sulfide, polycarbonate, polymethylmethacrylate, polyether, poly(ether-ether-ketone), polyether imide;polyacetal; and various kinds of thermoplastic elastomers of styrene,polyolefin, polyvinyl chloride, polyurethane, polyester, polyamide,polybutadiene, transpolyisoprene, fluororubber, chlorinatedpolyethylene, etc., and a copolymer, a blend, and a polymer alloypredominantly composed of them, one or more kinds of which may be mixedand used.

The (average) thicknesses of such substrates 1, 2 are each setappropriately depending on the constitutive materials, applications,etc. Although the thicknesses are not particularly limited, thethicknesses may be about 20-500 μm and preferably about 25-250 μm, whenthe substrates are flexible. Thus, it becomes possible to downsize (andespecially to slim) the electrophoretic display device 20 while matchingthe flexibility and strength of the electrophoretic display device 20 toeach other.

The first electrode 3 and second electrode 4, each forming a layer (afilm), are provided respectively on surfaces of the substrates 1, 2 onthe side of the electrophoretic dispersion 10 to be described later,i.e. on the bottom surface of the first substrate 1 and the top surfaceof the second substrate 2.

When a voltage is applied between the first electrode 3 and the secondelectrode 4, an electric field is produced therebetween, which acts onthe electrophoretic particles in the electrophoretic dispersion 10.

In this exemplary embodiment, the first electrode 3 is a commonelectrode, and the second electrode 4 is divided into separateelectrodes (pixel electrodes) 4X in a matrix (a rectangular array ofrows and columns). Each separate electrode 4X and a portion of the firstelectrode 3 which overlaps the separate electrode constitute a unitpixel.

Further, as shown in FIG. 1, TFT elements (switching elements) 8 aredisposed between the second electrode 4 and the second substrate 2 sothat the TFT elements are electrically connected corresponding to theseparate electrodes (driving electrodes) 4X. Therefore, the device isdesigned so that a voltage can be applied independently between theseparate electrodes 4X and the first electrode 3.

In this exemplary embodiment, the separate electrodes 4X are arranged ina matrix, and the TFT elements 8 are arranged in a matrix accordingly.

Also, the first electrode 3 may be divided into plural ones as are thesecond electrode 4.

The constitutive materials of the electrodes 3, 4 are not particularlylimited as long as the materials are substantially conductive. Forexample, the constitutive materials may be any of various conductivematerials including: a metal material of copper, aluminum, nickel,cobalt, platinum, gold, silver, molybdenum, or tantalum, or a metalalloy containing any of them; a carbon-based material of carbon black,carbon nanotube, or fullerene; an electron-conducting polymeric materialof polyacetylene, polypyrrole, polythiophene, polyaniline,poly(p-phenylene), poly(p-phenylene vinylene), polyfluorene,polycarbazole, polysilane, or the derivatives thereof, or the like; anion-conducting polymeric material prepared by dispersing an ionicsubstance in a matrix resin of polyvinyl alcohol, polycarbonate,polyethylene oxide, polyvinyl butyral, polyvinyl carbazole, vinylacetate, or the like, the ionic substance consisting of NaCl, LiClO₄,KCl, H₂O, LiCl, LiBr, LiI, LiNO₃, LiSCN, LiCF₃SO₃, NaBr, NaI, NaSCN,NaClO₄, NaCF₃SO₃, KI, KSCN, KClO₄, KCF₃SO₃, NH₄I, NH₄SCN, NH₄ClO₄,NH₄CF₃SO₃, MgCl₂, MgBr₂, MgI₂, Mg(NO₃)₂, MgSCN₂, Mg(CF₃SO₃)₂, CaBr₂,CaI₂, CaSCN₂, Ca(ClO₄)₂, Ca(CF₃SO₃)₂, ZnCl₂, ZnI₂, ZnSCN₂, Zn(ClO₄)₂,Zn(CF₃SO₃)₂, CuCl₂, CuI₂, CuSCN₂, Cu(ClO₄)₂, Cu(CF₃SO₃)₂, or the like;and a conductive oxide material of indium tin oxide (ITO),fluorine-doped tin oxide (FTO), tin oxide (SO₂), indium oxide (IO), orthe like. These constitutive materials may be used individually or in acombination of two or more kinds.

As other constitutive materials for the electrodes 3, 4, for example,various kinds of composite materials may be used respectively, to whichconductivity is imparted by mixing a conductive material (conductiveparticles) of gold, silver, nickel, carbon, or the like into anon-conductive material of glass material, rubber material, polymericmaterial, or the like.

Examples of such composite materials include, for example, a conductiverubber prepared by mixing a conductive material into a rubber material,a conductive adhesive or conductive paste prepared by mixing aconductive material into an adhesive composition of epoxy, urethane,acrylic, or the like, and a conductive resin prepared by mixing aconductive material into a matrix resin of polyolefin, polyvinylchloride, polystyrene, ABS resin, Nylon (polyamide), ethylene-vinylacetate copolymer, polyester, acrylic resin, epoxy-based resin,urethane-based resin, or the like.

The (average) thicknesses of such electrodes 3, 4 are each setappropriately depending on the constitutive materials, applications,etc. and they are not particularly limited, but suitably about 0.05-10μm, more suitably about 0.05-5 μm.

Of the substrates 1, 2 and the electrodes 3, 4, the substrate andelectrode disposed on the display side (i.e. the first substrate 1 andthe first electrode 3 in this exemplary embodiment) have each an opticaltransparency, i.e., they may be substantially transparent (colorless andtransparent, colored and transparent, or translucent). Thus, it becomespossible to visually recognize conditions of the electrophoreticparticles in the electrophoretic dispersion 10 to be described later,i.e. the information (picture image) displayed in the electrophoreticdisplay device 20.

The electrodes 3, 4 may each have, for example, a multilayer structure,as produced by the sequential stacking of a plurality of materials, inaddition to a single-layer structure composed of a single body of amaterial as mentioned above. Specifically, the electrodes 3, 4 may eachhave a single-layer structure composed of, for example, an ITO, or atwo-layer structure composed of an ITO layer and a polyaniline layer.

Further, between the first substrate 1 and the second substrate 2 and ina vicinity of a side portion of the electrophoretic display device 20,there may be provided a spacer 7 having the function of determining thedistance between the first electrode 3 and the second electrode 4.

In this exemplary embodiment, the spacer 7 is provided so as to surroundthe periphery of the electrophoretic display device 20 and the spaceralso has, as a sealing member, the function of defining (forming) asealed space 71 between the first substrate 1 and the second substrate2.

The constitutive materials for the spacer 7 include a resin material ofepoxy-based resin, acrylic resin, urethane-based resin, melamine-basedresin, phenol resin, or the like, and a ceramic material of silica,alumina, titania, or the like, for example. These constitutive materialsmay be used individually or in combination of two ore more kinds ofthem.

The (average) thickness of such spacer 7, i.e. the distance between theelectrodes 3 and 4 (inter-electrode distance), is not particularlylimited, but suitably about 10-500 μm, more suitably about 20-100 μm.

The spacer 7 is not limited to a configuration such that it is providedsurrounding the periphery of the electrophoretic display device 20. Forexample, a plurality of spacers 7 may be provided in vicinities of theside portion of the electrophoretic display device 20 at givenintervals. In this case, the gaps between the. spacers 7 may be sealedwith the other sealant (sealing material).

The sealed space 71 (the cell's inside space defined by one pair of thesubstrates and the spacer 7) contains (is filled with) theelectrophoretic dispersion 10 of an aspect of the invention. Thus, theelectrophoretic dispersion 10 is in contact with the first electrode 3and the second electrode 4 directly.

The electrophoretic dispersion (dispersion for electrophoretic displayunits) 10 is prepared by dispersing electrophoretic particles, which areelectrophoretically migrated under an influence of an electric field,into the liquid phase insulative dispersion medium 6.

In an aspect of the invention, the electrophoretic particles includeinorganic particles, and resin particles dyed a color different fromthat of the inorganic particles and having an electrical polarityopposite to that of the inorganic particles.

The inorganic particles and resin particles are combined and used aselectrophoretic particles, whereby the aggregation of theelectrophoretic particles can be reduced or prevented.

In this exemplary embodiment, two kinds of electrophoretic particles,i.e. white inorganic particles 5 a and colored resin particles 5 b, areused.

The inorganic particles 5 a and the resin particles 5 b are notparticularly limited and therefore any kind of particles may be used asthe inorganic and resin particles as long as the particles each can beelectrically charged and electrophoretically migrated in the liquidphase dispersion medium 6 under an influence of an electric field.

The inorganic particles 5 a may contain, for example, titanium oxide(titania), or a pigment, such as prussian blue, ultramarine blue,phthalocyanine blue, chrome yellow, cadmium yellow, lithopone, molybdateorange, fast yellow, benzimidazoline yellow, flavanthrone yellow,naphthol yellow, benzimidazoline orange, perinone orange, iron red,cadmium red, Madder Lake, naphthol red, dioxazine violet, alkali blue,cerulean blue, emerald green, phthalocyanine green, pigment green,cobalt green, or aniline black. Otherwise the inorganic particles maycontain a compound, e.g. hydrozincite, barium sulfate, chromium oxide,calcium carbonate, gypsum, white lead, carbon black, or iron black.

Of these materials, the inorganic particles 5 a may be made mainly fromtitanium oxide. Such titanium oxide-based inorganic particles 5 a have ahigh whiteness degree and the particles have an especially-lowcohesiveness with respect to the resin particles 5 b.

In addition, surfaces of the inorganic particles 5 a may have alreadyundergone a process to increase the dispersibility thereof with respectto the liquid phase dispersion medium 6. This enhances thedispersibility of the inorganic particles 5 a with respect to the liquidphase dispersion medium 6, and thus it becomes possible to reduce orprevent the aggregation with the resin particles 5 b.

The surface treatment for the inorganic particles 5 a may be a processby a surface-treating agent, such as a silane-based coupling agent, atitanate-based coupling agent, an aluminum-based coupling agent, or azirconium-based coupling agent.

Especially, the titanate-based coupling agent (“KR TTS” manufactured byAjinomoto Co., Inc.), and the aluminum-based coupling agent (“AL-M”manufactured by Ajinomoto Co., Inc.) may be used as the surface-treatingagent.

The resin particles 5 b may be particles produced by, for example,emulsion polymerization.

The resin materials, which the resin particles 5 b can be made from,include acrylic resin, urethane-based resin, urea-based resin,epoxy-based resin, melamine resin, polystyrene, polyester, anddivinylbenzene, for example. These materials may be used individually orin a combination of two or more kinds.

Of these materials, the materials containing acrylic resin as its maincomponent are preferable for the resin material which the resinparticles 5 b are made from. The aggregation of the resin particles 5 bwith the inorganic particles 5 a can be reduced or prevented by makingthe resin particles 5 b mainly from acrylic resin.

Further, the above resin may have a molecular structure containing apolar group, such as a hydroxyl group, an amino group, or a carboxylgroup. When such a polar group is introduced, the polar group isintroduced in the molecular structure of the resin. Thus the resin isinsolubilized with respect to the solvent. As a result, the resistanceproperty of the resin particles 5 b with respect to the liquid phasedispersion medium 6 can be increased.

From this point of view, the polar group may be at least one of ahydroxyl group and an amino group, and preferably an amino group.

In consideration of the foregoing, the resin may be an acrylic resinhaving, as its polar group, at least one of a hydroxyl group and anamino group.

Such acrylic resin can be obtained, for example, by copolymerizing anacrylic monomer having a polar group with an acrylic resin andintroducing the polar group in the resin. This method makes it possibleto obtain an acrylic resin having a polar group relatively readily at ahigh yield.

Appropriately setting the amount of the introduced polar group allowsthe adjustment of the electrification of the resin particles 5 b in theliquid phase dispersion medium 6.

In addition, the resin particles 5 b are dyed any one of red, green,blue, and black, for example, by mixing colorants of dye, pigment, etc.Thus, the electrophoretic display device 20 can display in the color ofthe inorganic particles 5 a, the color of the resin particles 5 b, andmixed colors thereof.

The average particle sizes of such inorganic particles 5 a and resinparticles 5 b may satisfy the following relation. Specifically, when theinorganic particles 5 a have an average particle size of A[μm] and theresin particles 5 b have an average particle size of B[μm], it ispreferable to satisfy a relation such that B/A falls in 1.5-200, andmore preferably to satisfy a relation such that B/A falls in 5-50. Thus,it becomes possible to effectively reduce or prevent the aggregation ofthe inorganic particles 5 a and resin particles 5 b while maintainingthe dispersibilities of the particles 5 a, 5 b in the liquid phasedispersion medium 6 suitably.

Concretely, the average particle size B of the resin particles 5 b maybe about 0.5-20 μm, and preferably 2-10 μm. When the average particlesize B of the resin particles 5 b is within the above range, theabove-mentioned effect can be achieved more suitably. The effects, suchas the effect of preventing the thickness of the electrophoretic displaydevice 20 from being increased and the effect of preventing thereduction in production efficiency, can be achieved.

In the case where inorganic particles 5 a have undergone surfacetreatment with a surfactant (the surfactant has been adsorbed on thesurfaces of the inorganic particles 5 a), when the average particle sizeB of the resin particles 5 b is excessively small, the resin particles 5b can be trapped by hydrophobic chains of the surfactant. Thus theaggregation of the inorganic particles 5 a and the resin particles 5 bcan occur. However, even in the case where the inorganic particles 5 ahave undergone surface treatment with a surfactant, the aggregation ofthe inorganic particles 5 a and the resin particles 5 b can be reducedor prevented effectively when the average particle size B of the resinparticles 5 b is equal to or larger than 0.5 μm (particularly, equal toor larger than 2 μm).

Also, from this point of view, the surface treatment of the inorganicparticles 5 a by a surfactant may be omitted.

The average particle size A of the inorganic particles 5 a may be about0.1-10 μm, and more preferably about 0.1-7.5 μm. Particularly it ispreferable that the average particle size A is about 0.2-0.3 μm.

Further, the specific gravities of the particles 5 a, 5 b may berespectively set so that they are substantially equal to the specificgravity of the liquid phase dispersion medium 6. This allows theparticles 5 a, 5 b to stay at fixed locations in the liquid phasedispersion 6 for a long time, even after the application of a voltagebetween the electrodes 3 and 4 has been stopped. The informationdisplayed by the electrophoretic display device 20 is to be kept for along time.

The insulative liquids may be used for the liquid phase dispersionmedium 6. Such liquid phase dispersion mediums 6 include, for example,alcohols of methanol, ethanol, isopropanol, butanol, octanol, ethyleneglycol, diethylene glycol, glycerin, etc., cellosolves of methylcellosolve, ethyl cellosolve, phenyl cellosolve, etc., esters of methylacetate, ethyl acetate, butyl acetate, ethyl formate, etc., ketones ofacetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone,methyl isopropyl ketone, cyclohexanone, etc., aliphatic hydrocarbons(paraffinic hydrocarbons) of pentane, hexane, octane, etc., alicyclichydrocarbons of cyclohexane, methylcyclohexane, etc., aromatichydrocarbons of benzene, toluene, xylene, hexylbenzene, butylbenzene,octylbenzene, nonylbenzene, benzenes having long-chain alkyl groups(alkylbenzene derivatives) such as decylbenzene, undecylbenzene,dodecylbenzene, tridecylbenzene, and tetradecylbenzene, etc.,halogenated hydrocarbons of methylene chloride, chloroform, carbontetrachloride, 1,2-dichloroethane, etc., heterocyclic aromatic compoundsof pyridine, pyrazine, furan, pyrrole, thiophene, methylpyrrolidone,etc., nitriles of acetonitrile, propionitrile, acrylonitrile, etc.,amides of N,N-dimethylformamide, N,N-dimethylacetamide, etc.,carboxylate, and other oils. These may be used separately or in amixture thereof.

Of these substances, an alkylbenzene derivative (especiallydodecylbenzene) is suitable for the liquid phase dispersion medium 6. Analkylbenzene derivative is preferable because the raw material thereofcan be obtained at relatively low cost and readily and. provides a highdegree of safety.

To the liquid phase dispersion medium 6 (electrophoretic dispersion 10),various kinds of additives, i.e. a charging-control agent composed ofparticles of an electrolyte, a surfactant, a metal soap, a resinmaterial, a rubber material, oils, a varnish, a compound, or the like, adispersing agent of a titanium-based coupling agent, an aluminum-basedcoupling agent, a silane-based coupling agent, or the like, a lubricant,a stabilizing agent, etc. may be added on an as-needed basis, forexample.

Further, in the liquid phase dispersion medium 6, any of ananthraquinone-based dye, an azo-based dye, an indigoid-based dye, atriphenylmethane-based dye, a pyrazolone-based dye, a stilbene-baseddye, a diphenylmethane-based dye, a xanthene-based dye, analizarin-based dye, an acridine-based dye, a quinonimine-based dye, athiazole-based dye, a methine-based dye, a nitro-based dye, anitroso-based dye, and the like may be dissolved on an as-needed basis.

In an electrophoretic display device 20 like this, when a TFT element 8is turned on, a voltage is applied between the separate electrode 4Xcorresponding to the TFT element 8 in ON state and the first electrode3. During this time, the particles 5 a, 5 b are each electrophoreticallymigrated toward one of the electrodes according to the electric fieldgenerated between the separate electrode 4X and the first electrode 3.

For example, in the case where the positively-charged inorganicparticles 5 a and negatively-charged resin particles 5 b are used, whena separate electrode 4X is at a positive potential, the inorganicparticles 5 a are moved toward the first electrode 3 to be accumulatedon the first electrode 3, whereas the resin particles 5 b are movedtoward the separate electrode 4X to be accumulated on the separateelectrode 4X, as shown in FIG. 2A. Thus, viewing the electrophoreticdisplay device 20 from above (i.e. from the display side), the color ofthe inorganic particles 5 a is to be observed.

Conversely, when the separate electrode 4X is at a negative potential,the inorganic particles 5 a are moved toward the separate electrode 4Xto be accumulated on the separate electrode 4X, whereas the resinparticles 5 b are moved toward the first electrode 3 and thenaccumulated on the first electrode 3, as shown in FIG. 2B. Accordingly,viewing the electrophoretic display device 20 from above (i.e. from thedisplay side), the color of the resin particles 5 b is to be observed.

Therefore, desired information (picture image) can be displayed on thedisplay side of the electrophoretic display device 20 according tocombinations of the color of the inorganic particles 5 a and the colorof the resin particles 5 b by turning each TFT element 8 on/off orapplying a voltage between the corresponding separate electrode 4X andthe first electrode 3, or setting the polarity of each separateelectrode 4X appropriately.

An electrophoretic display device 20 like this can be manufactured, forexample, as follows.

[A1] First, a first electrode 3 and TFT elements 8 and separateelectrodes 4X (constituting a second electrode 4) are formedrespectively on a first substrate 1 and on a second substrate 2 usingthe film-forming methods.

[A2] Second, the first substrate 1 with the first electrode 3 and thesecond substrate 2 with the TFT elements 8 and the separate electrodes4X are bonded through a spacer 7.

In this step, a through-hole to fill an electrophoretic dispersion 10into the sealed space 71 is formed in a portion of the spacer 7.

[A3] Next, the electrophoretic dispersion 10 is filled into the sealedspace 71 through the through-hole and then the through-hole is sealed.

In the electrophoretic display device 20 as described above, theaggregation of the inorganic particles 5 a and the resin particles 5 bare reduced or prevented. Therefore, stable display performance can beoffered for a long time.

Second Exemplary Embodiment

Now, a second exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 3 is a schematic showing (or partially showing) the secondexemplary embodiment of the electrophoretic display device of theinvention. FIG. 4 is an illustration showing a step of a manufacturingprocess of the electrophoretic display device illustrated in FIG. 3. InFIG. 3, the first substrate and the first electrode are omitted.

The electrophoretic display device of the second exemplary embodimentwill be described below with the focus on the differences from the firstexemplary embodiment, and the descriptions of like matters are to beomitted.

The electrophoretic display device 20 of the second exemplary embodimentis identical to the electrophoretic display device 20 of the firstexemplary embodiment except that the electrophoretic dispersion 10 isdistributed and placed in given places.

As shown in FIG. 3, in the second exemplary embodiment the separateelectrodes 4X are each shaped into a hexagon in its two-dimensionalshape and have partitions 11 provided upright along edge portions of theseparate electrodes 4X. Thus, the partitions 11 have generally ahoneycomb form.

In this configuration, spaces surrounded by partitions 11 (the spacespartitioned off) each constitute a cell space 12. Moreover, the cellspaces 12 are filled with an electrophoretic dispersion 10 as describedabove. The electrophoretic dispersion 10 is thus distributed.

As described above, each of the separate electrodes 4X is electricallyconnected with a TFT element 8. Accordingly, one TFT element 8 isprovided for each of the cell spaces 12.

As the constitutive material of the partitions 11, the resin materials(hardening resins), e.g. epoxy-based resin, silicon resin,melamine-based resin, urea-based resin, acrylic resin, and phenol resin,may be used individually or in a combination of two or more kinds.

In addition, the height of the partitions 11 is set to aninter-electrode distance as described above.

In the second exemplary embodiment, the cell spaces 12 slantwise arrayedin a line are filled with the electrophoretic dispersion 10 containingresin particles 5 b having the same color. Specifically, a line composedof a series of cell spaces 12 filled with a red electrophoreticdispersion 10 a, a line composed of a series of cell spaces 12 filledwith a green electrophoretic dispersion 10 b, and a line composed of aseries of cell spaces 12 filled with a blue electrophoretic dispersion10 c, are cyclically provided in turn.

This configuration allows the electrophoretic display device 20 of thesecond exemplary embodiment to display a set of desired information (apicture image) in multiple colors (in color).

An electrophoretic display device 20 like this can be manufactured, forexample, as follows.

[B1] The same step as the above step [A1] is carried out.

Next, partitions 11 are formed along the edge portions of the separateelectrodes 4X. The partitions 11 may be formed, for example, by: amethod by which a liquid containing a hardening resin precursor issupplied by a coating method (ink-jet method, printing, etc.) and thenhardened; or a photolithography.

Then, spaces surrounded by the partitions 11 (cell spaces 12) are filledwith an electrophoretic dispersion 10. While various methods may be usedto fill the cell spaces 12 with the electrophoretic dispersion 10 theprocess may be performed by a process using a dispenser or the ink-jetmethod. According to such method, the electrophoretic dispersion 10 canbe filled into the cell spaces 12 more readily and reliably.

FIG. 4 shows a method of filling the electrophoretic dispersion 10 intothe cell spaces 12 by the ink-jet method. As shown by the drawing, inthe ink-jet method, the electrophoretic dispersion 10 (dispersion inkfor electrophoretic display devices) is discharged from an end portionof a nozzle 100 as a droplet, and the droplet impinges on the separateelectrode 4X. The discharge operation is carried out for each cell space12 (separate electrode 4X), whereby the cell spaces 12 are filled withthe electrophoretic dispersion 10 (10 a for red, 10 b for green, 10 cfor blue).

[B2] Next, the first substrate 1 with the first electrode 3 and thesecond substrate 2 with the TFT elements 8, the separate electrodes 4X,the partitions 11, and the electrophoretic dispersion 10 are bondedthrough the spacer 7.

In this exemplary embodiment, the partitions 11 can be enhanced so thatit has the same function as that of the spacer 7. In this case, thespacer 7 may be omitted if required.

Also the electrophoretic display device 20 of the second exemplaryembodiment can provide the same effect and advantage as those of thefirst exemplary embodiment.

Third Exemplary Embodiment

Now, a third exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 5 is a schematic showing (or partially showing) the third exemplaryembodiment of the electrophoretic display device of the invention.

The electrophoretic display device of the third exemplary embodimentwill be described below with the focus on the differences from the firstand second exemplary embodiments, and the descriptions of like mattersare to be omitted.

The electrophoretic display device 20 of the third exemplary embodimentis identical to the electrophoretic display device 20 of the secondexemplary embodiment except for the layout pattern of theelectrophoretic dispersion 10.

As shown in FIG. 5, in the electrophoretic display device 20 of thethird exemplary embodiment, three cell spaces 12 adjacent to each otherare respectively filled with a red electrophoretic dispersion 10 a, agreen electrophoretic dispersion 10 b, and a blue electrophoreticdispersion 10 c.

In such configuration, a combination of three cell spaces 12 constitutesone pixel.

In an electrophoretic display device 20 like this, I: in the conditionwhere all of red (R), green (G), and blue (B) are displayed, the pixelis changed into black, II: in the condition where the one of red, green,and blue is displayed, the pixel is changed into the one color, III: inthe condition where any two of red, green, and blue are displayed, thepixel is of a mixed color of the two colors, IV: in the case where allof the colors are not displayed, the pixel is changed into white whenthe inorganic particles are of white (titania particles, for example).The electrophoretic display device 20 of the third exemplary embodimentis thus capable of providing display in multiple colors.

Also the electrophoretic display device 20 of the third exemplaryembodiment can provide the same effect and advantage as those of thefirst and second exemplary embodiments.

Fourth Exemplary Embodiment

Now, a fourth exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 6 is a schematic showing (or partially showing) the fourthexemplary embodiment of the electrophoretic display device of theinvention.

The electrophoretic display device of the fourth exemplary embodimentwill be described below with the focus on the differences from the firstto third exemplary embodiments, and the descriptions of like matters areto be omitted.

The electrophoretic display device 20 of the fourth exemplary embodimentis identical to the electrophoretic display device 20 of the thirdexemplary embodiment except that four kinds of electrophoreticdispersions 10 are used.

As shown in FIG. 6, in the electrophoretic display device 20 of thefourth exemplary embodiment, adjacent four cell spaces 12 arerespectively filled with a red electrophoretic dispersion 10 a, a greenelectrophoretic dispersion 10 b, a blue electrophoretic. dispersion 10c, and a black electrophoretic dispersion 10 d.

In such a configuration, a combination of four cell spaces 12constitutes one pixel.

This configuration allows the electrophoretic display device 20 to makeblack more brilliant in displayed information (a picture image).

Also the electrophoretic display device 20 of the fourth exemplaryembodiment can provide the same effect and advantage as those of thefirst to third exemplary embodiments.

Fifth Exemplary Embodiment

Now, a fifth exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 7 is a schematic showing (or partially showing) the fifth exemplaryembodiment of the electrophoretic display device of the invention.

The electrophoretic display device of the fifth exemplary embodimentwill be described below with the focus on the differences from the firstand second exemplary embodiments, and the descriptions of like mattersare to be omitted.

The electrophoretic display device 20 of the fifth exemplary embodimentis identical to the electrophoretic display device 20 of the secondexemplary embodiment except for the general shape of the partitions 11.

As shown in FIG. 7, in the electrophoretic display device 20 of thefifth exemplary embodiment, the separate electrodes 4X (and cell spaces12) are each shaped into a square in its two-dimensional shape, and thepartitions 11 are generally shaped into a grid pattern.

In this configuration, continuously-arranged three cell spaces 12 arerespectively filled with a red electrophoretic dispersion 10 a, a greenelectrophoretic dispersion 10 b, and a blue electrophoretic dispersion10 c.

In such configuration, a combination of three cell spaces 12 constitutesone pixel.

Also the electrophoretic display device 20 of the fifth exemplaryembodiment can provide the same effect and advantage as those of thefirst and second exemplary embodiments.

Sixth Exemplary Embodiment

Now, a sixth exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 8 is a schematic showing (or partially showing) the sixth exemplaryembodiment of the electrophoretic display device of the invention.

The electrophoretic display-device of the sixth exemplary embodimentwill be described below with the focus on the differences from thefirst, second and fifth exemplary embodiments, and the descriptions oflike matters are to be omitted.

The electrophoretic display device 20 of the sixth exemplary embodimentis identical to the electrophoretic display device 20 of the fifthexemplary embodiment except for the general shape of the partitions 11.

As shown in FIG. 8, in the electrophoretic display device 20 of thesixth exemplary embodiment, the separate electrodes 4X (and cell spaces12) are each shaped into a rectangle in its two-dimensional shape, andthe partitions 11 are generally shaped into a grid pattern.

Also the electrophoretic display device 20 of the sixth exemplaryembodiment can provide the same effect and advantage as those of thefirst, second, and fifth exemplary embodiments.

Seventh Exemplary Embodiment

Now, a seventh exemplary embodiment of the electrophoretic displaydevice of the invention will be described.

FIG. 9 is a schematic showing (or partially showing) the seventhexemplary embodiment of the electrophoretic display device of theinvention.

The electrophoretic display device of the seventh exemplary embodimentwill be described below with the focus on the differences from thefirst, second and fifth exemplary embodiments, and the descriptions oflike matters are to be omitted.

The electrophoretic display device 20 of the seventh exemplaryembodiment is identical to the electrophoretic display device 20 of thefifth exemplary embodiment except for the constitutive unit of onepixel.

As shown in FIG. 9, in the electrophoretic display device 20 of theseventh exemplary embodiment, a combination of 3×3 cell spaces 12 (ninecell spaces in total) constitute one pixel.

Such configuration allows the electrophoretic display device 20 todisplay an image by an area ratio gray-scale method and to display animage with a 4-step gradation, which makes it possible to display a setof information (a picture image) further nearly in full color.

Also the electrophoretic display device 20 of the seventh exemplaryembodiment can provide the same effect and advantage as those of thefirst, second, and fifth exemplary embodiments.

Eighth Exemplary Embodiment

Now, an eighth exemplary embodiment of the electrophoretic displaydevice of the invention will be described.

FIG. 10 is a schematic showing (or partially showing) the eighthexemplary embodiment of the electrophoretic display device of theinvention. In FIG. 10, the first substrate and first electrode areomitted.

The electrophoretic display device of the eighth exemplary embodimentwill be described below with the focus on the differences from the firstand second exemplary embodiments, and the descriptions of like mattersare to be omitted.

The electrophoretic display device 20 of the eighth exemplary embodimentis identical to the electrophoretic display device 20 of the secondexemplary embodiment except that the electrophoretic dispersion 10 isencapsulated in microcapsules 40.

As shown in FIG. 10, in the electrophoretic display device 20 of theeighth exemplary embodiment, a line composed of a series of redmicrocapsules 40 a encapsulating a red electrophoretic dispersion 10 a,a line composed of a series of green microcapsules 40 b encapsulating agreen electrophoretic dispersion 10 b, and a line composed of a seriesof microcapsules 40 c encapsulating a blue electrophoretic dispersion 10c, are cyclically provided in turn.

The constitutive materials for the microcapsules 40 (40 a-40 c) are notparticularly limited, but the materials include, for example, variouskinds of resin materials, such as a composite material of acacia gum andgelatin, urethane-based resin, melamine-based resin, urea resin,polyamide, and polyether. These materials may be used individually or ina combination of two or more kinds.

The preparation technique of the microcapsules 40 (i.e. the method ofencapsulating the electrophoretic dispersion 10 in the microcapsules 40)is not particularly limited, but various encapsulation techniques, e.g.interface polymerization, in-situ polymerization, phase isolation (orcoacervation), interface precipitation, and spray drying, may be used asthe preparation technique. The above-described encapsulation techniquesmay be appropriately selected according to the constitutive material ofthe microcapsules 40, etc.

Microcapsules 40 like this may be substantially uniform in size. Thisallows the electrophoretic display device 20 to offer better displayperformance. The microcapsules 40 of a uniform size can be obtained, forexample, by filtration or specific gravity difference classification.

The size (average particle size) of the microcapsules 40 is notparticularly limited, but may be about 10-150 μm, and preferably about30-100 μm, generally.

A binder material may be supplied in periphery portions of themicrocapsules 40 in a gap between the first electrode 3 and the secondelectrode 4.

The binder material is to be supplied, for example, for the purposes offixing the microcapsules 40, keeping the insulating property between theelectrodes 3 and 4, etc. Thus, the durability and reliability of theelectrophoretic display device 20 can be further increased.

For the binder material, resin materials superior in its affinity(adhesion) with respect to the electrodes 3, 4 and microcapsules 40 andin its insulating property are may be used.

The resin materials are not particularly limited, but they include, forexample, polyethylene, chlorinated polyethylene, ethylene-vinyl acetatecopolymer, ethylene-ethyl acrylate copolymer, polypropylene, ABS resin,methyl methacrylate resin, vinyl chloride resin, vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinylchloride-acryl ester copolymer, vinyl chloride-methacrylic acidcopolymer, vinyl chloride-acrylonitrile copolymer, ethylene-vinylalcohol-vinyl chloride copolymer, propylene-vinyl chloride copolymer,vinylidene chloride resin, vinyl acetate resin, polyvinyl alcohol,polyvinyl formal, thermoplastic resins, such as cellulose-based resin,polyamide-based resins, polyacetal, polycarbonate, polyethyleneterephthalate, polybutylene terephthalate, polyphenylene oxide,polysulfone, polyamideimide, polyaminobismaleimide, polyether sulfone,polyphenylene sulfone, polyarylate, graft polymerized polyphenyleneether, poly(ether-ether-ketone), polymeric materials such as polyetherimide, polytetrafluoroethylene, polyfluoroethylenepropylene,tetrafluoroethylene-perfluoroalkoxyethylene copolymer,ethylene-tetrafluoroethylene copolymer, poly(vinylidene fluoride),polytrifluoroethylene chloride, fluorine-based resins of fluororubber,etc., silicone-based resins, and silicone resins of silicone rubber,etc., in addition to methacrylic acid-styrene copolymer, polybutylene,and methyl methacrylate-butadiene-styrene copolymer. These materials maybe used individually or in a combination of two or more kinds.

The binder material may be set to have a dielectric constantsubstantially equal to that of the liquid phase dispersion medium 6.Therefore, a dielectric constant regulant of, for example, an alcoholsuch as 1,2-butanediol, or 1,4-butanediol, a ketone, or carboxylate, maybe added into the binder material.

An electrophoretic display device 20 like this can be manufactured, forexample, as follows.

[C1] The same step as in the step [A1] is carried out.

Next, an adhesive is supplied on a target separate electrode 4X (secondelectrode 2), followed by supplying, for example, red microcapsules 40 aand hardening the adhesive thereby to fix the microcapsules 40 a on theseparate electrode 4X. Thus, the microcapsules 40 a are electricallyconnected to the intended TFT element 8.

This operation (step) is repeated the number of times depending on thekinds of the microcapsules 40 of different colors (40 b, 40 c).

According to such method, the microcapsules 40 can be placed on thesecond substrate 2 more readily and reliably.

[C2] Next, the first substrate 1 with the first electrode 3 issuperposed on the second substrate and bonded therewith so that thefirst electrode 3 contacts the microcapsules 40.

Also the electrophoretic display device 20 of the eighth exemplaryembodiment can provide the same effect and advantage as those of thefirst and second exemplary embodiments.

Now, it is noted that the layout patterns of the third to seventhexemplary embodiments may be applied to layout patterns for themicrocapsules 40 (40 a, 40 b, and 40 c).

Ninth Exemplary Embodiment

Now, a ninth exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 11 is a schematic showing (or partially showing) the ninthexemplary embodiment of the electrophoretic display device of theinvention.

The electrophoretic display device of the ninth exemplary embodimentwill be described below with the focus on the differences from thefirst, seventh and eighth exemplary embodiments, and the descriptions oflike matters are to be omitted.

The electrophoretic display device 20 of the ninth exemplary embodimentis identical to the electrophoretic display devices 20 of the seventhand eighth exemplary embodiments except that the microcapsules 40 arecontained (or accommodated) in the cell spaces 12.

The electrophoretic display device 20 of the ninth exemplary embodimentis a combination of the configurations of the electrophoretic displaydevice 20 of the seventh exemplary embodiment and the electrophoreticdisplay device 20 of the eighth exemplary embodiment.

Such configuration allows the microcapsules 40 to be placed in positionmore precisely.

Also the electrophoretic display device 20 of the ninth exemplaryembodiment can provide the same effect and advantage as those of thefirst, seventh, and eighth exemplary embodiments.

Tenth Exemplary Embodiment

Now, a tenth exemplary embodiment of the electrophoretic display deviceof the invention will be described.

FIG. 12 is a longitudinal cross-sectional schematic showing (orpartially showing) the tenth exemplary embodiment of the electrophoreticdisplay device of the invention.

The electrophoretic display device of the tenth exemplary embodimentwill be described below with the focus on the differences from the firstand eighth exemplary embodiments, and the descriptions of like mattersare to be omitted.

The electrophoretic display device 20 of the tenth exemplary embodimentis identical to the electrophoretic display device 20 of the eighthexemplary embodiment except that one microcapsule 40 is placed on twoseparate electrodes 4X.

In such a electrophoretic display device 20, as shown in FIG. 12, theelectrophoretic display device 20 is viewed from above (i.e. from thedisplay side), the color of the inorganic particles 5 a (white) for theleft side microcapsule 40, the color resulting from the mix in colors ofthe inorganic particles 5 a and the resin particles 5 b (a secondarycolor) for the center microcapsule 40, and the color of the resinparticles 5 b (not colorless) for the right side microcapsule 40 arerespectively to be observed depending on combinations of the polaritiesof the separate electrodes 4X.

This configuration allows electrophoretic display device 20 to displayan image with a higher-level gray scale.

Also the electrophoretic display device 20 of the tenth exemplaryembodiment can provide the same effect and advantage as those of thefirst and eighth exemplary embodiments.

Electrophoretic display devices 20 as described above can beincorporated in various electronic systems. The electronic system of anaspect of the invention, which has such electrophoretic display device20, will be described below.

Electronic Paper

Now, an exemplary embodiment in the case where the electronic system ofan aspect of the invention is applied to an electronic paper will bedescribed.

FIG. 13 is a schematic showing an exemplary embodiment in the case wherethe electronic system of an aspect of the invention is applied to anelectronic paper.

The electronic paper 600 illustrated in FIG. 13 includes a main body 601composed of a rewritable sheet having a paper-like texture andflexibility, and a display unit 602.

In such electronic paper 600, the display unit 602 is composed of anelectrophoretic display device 20 as described above.

Display

Now, an exemplary embodiment in the case where the electronic system ofthe invention is applied to a display will be described.

FIGS. 14A and 14B are each an illustration showing an exemplaryembodiment in the case where the electronic system of the invention isapplied to a display. Of these drawings, FIG. 14A is a cross-sectionalschematic and FIG. 14B is a schematic.

The display (display device) 800, illustrated in FIGS. 14A and 14B,includes a main body section 801 and an electronic paper 600 removablyprovided on the main body section 801. The electronic paper 600 is ofthe above-described configuration, and is the same as the electronicpaper illustrated in FIG. 13 in its configuration.

The main body section 801 has an inlet 805 formed in a side portionthereof (on the right side of FIGS. 14A, 14B), and two pairs oftransporting rollers 802 a, 802 b provided inside the body section. Fromthe inlet the electronic paper 600 can be inserted. When the electronicpaper 600 is inserted in the main body section 801 through the inlet805, the electronic paper 600 is attached to the main body section 801 athe condition where the paper is held by the pairs of transportingrollers 802 a, 802 b therebetween.

Also, the main body section 801 has a rectangular opening 803 formed onthe display side thereof (on the near side of the drawing sheet of FIG.14B). A transparent glass panel 804 is fitted in the opening 803. Thus,it becomes possible to visually identify the electronic paper 600attached to the main body section 801, from the outside of the main bodysection 801. That is to say, in the display 800 the display side isarranged so that the electronic paper 600 attached to the main bodysection 801 is visually identified through the transparent glass panel804.

The electronic paper 600 has a terminal section 806 provided in aleading end portion in the insert direction of the electronic paper 600(on the left side of FIGS. 14A, 14B). The main body section 801 has asocket 807 provided inside, to which the terminal section 806 isconnected in the condition where the electronic paper 600 is attached tothe main body section 801. A controller 808 and an operation section 809are electrically connected to the socket 807.

In the display 800, the electronic paper 600 is removably attached tothe main body section 801. Therefore it can be detached from the mainbody section 801, carried like that, and used.

Also, in a display 800 like this, the electronic paper 600 is composedof an electrophoretic display device 20 as described above.

The electronic system of an aspect of the invention is not limited tothe above application. Its applications may include, for example, atelevision set, a digital still camera, viewfinder type anddirect-monitoring type video tape recorders, a car navigation system, apager, an electronic datebook, an electronic calculator, an electronicnewspaper, an electronic book, an electronic notebook, a word processor,a personal computer, a workstation, a cell phone, a picture telephone, aPOS terminal, and a system with a touch panel. The electrophoreticdisplay device 20 of an aspect of the invention can be applied to thedisplay sections of these electronic systems.

While the electrophoretic dispersion, electrophoretic display device,the method of manufacturing the electrophoretic display device, and theelectronic system of an aspect of the invention have been describedabove based on the exemplary embodiments shown in the drawings, theinvention is not limited to the exemplary embodiments.

The electrophoretic display device of an aspect of the invention may bea device produced by combining any two or more of the first to tenthexemplary embodiments in their configurations (features).

While in the exemplary embodiments the devices having a configurationsuch that a pair of electrodes are provided opposite each other havebeen shown, the electrophoretic display device of an aspect of theinvention may be applied to an electrophoretic display device having aconfiguration such that a pair of electrodes are provided on the samesubstrate.

EXAMPLES

Examples of an aspect of the invention are described below.

Example 1

1. Preparation of the Electrophoretic Dispersion

A red electrophoretic dispersion was prepared by ultrasonicallydispersing 8 g of acrylic particles colored red (“CHEMISNOW,”manufactured by Soken Chemical & Engineering Co., Ltd.) and 8 g oftitania particles (“CR-90,” manufactured by Ishihara Sangyo Kaisha,Ltd.) in 80 ml of dodecylbenzene, the titania particles being processedwith a surface-treating agent manufactured by Ajinomoto Co., Inc.

The acrylic particles having an average particle size of 4 μm and thetitania particles having an average particle size of 0.2-0.3 μm wereused here.

In the same way, a green electrophoretic dispersion and a blueelectrophoretic dispersion were prepared.

“CHEMISNOW,” manufactured by Soken Chemical & Engineering Co., Ltd. wereused for the acrylic particles colored green, and also “CHEMISNOW,”manufactured by Soken Chemical & Engineering Co., Ltd. were used for theacrylic particles colored blue.

2. Manufacturing of the Electrophoretic Display Device

First, a substrate having thin film transistor elements (TFT glasssubstrate) was obtained. The substrate was prepared by the same processas that for preparing TFT substrates used to manufacture liquid crystaldisplays.

Then, a photoresist layer was formed by coating a resist material on theTFT glass substrate, exposing and developing the resist material.Grooves arranged in an intended partition pattern (a grid patternillustrated in FIG. 7) were thus formed in the photoresist layer.

Next, the grooves were supplied with a two-part curable silicone resin(containing two components “TSE 3450(A)” and “TSE 3450(B)” manufacturedby Toshiba Silicones) and the resin was then cured. Thereafter, theresulting photoresist layer was exfoliated and removed from thesubstrate, whereby partitions extending upward from the substrate wereformed.

The partitions had a height of 30 μm and a width of 10 μm and weretwo-dimensionally arranged at a pitch of 100 μm.

Then, the red, green, blue electrophoretic dispersions were filled inthe corresponding spaces defined by the partitions (cell spaces) with alayout pattern illustrated in FIG. 7 using an ink-jet device (i.e. acommercial ink-jet printer which had been modified).

Next, a glass substrate with an ITO layer on an entire surface thereofwas placed over the cell spaces, and then the periphery portion of thepaired substrates was sealed with an epoxy resin (“ARALBOND,”manufacture by Ciba-Geigy Japan Ltd.) while forces were applied to thesubstrates. Thus, the electrophoretic display device was obtained.

When the terminal section of the resulting electrophoretic displaydevice was coupled with a power source through lines to try activatingthe device, the display device could be activated in multiple colorsincluding black, red, green, blue, and white. Also, the display devicecould be activated in a secondary color produced by these colors.

Example 2

The electrophoretic display device was manufactured by the same processas that of Example 1 except that the partitions were different in shapeand electrophoretic dispersions of four colors were used.

1. Preparation of the Electrophoretic Dispersion

In the same way as in Example 1, a red electrophoretic dispersion, greenelectrophoretic dispersion, blue electrophoretic dispersion, and blackelectrophoretic dispersion were prepared.

For the acrylic particles colored black, “CHEMISNOW” manufactured bySoken Chemical & Engineering Co., Ltd. was used.

2. Manufacturing of the Electrophoretic Display Device

The partitions were shaped into a honeycomb form as illustrated in FIG.6. Then the red, green, blue, and black electrophoretic dispersions werefilled in cell spaces with the layout pattern illustrated in FIG. 6.

As a result, an electrophoretic display device superior in display inblack to that in Example 1 could be obtained.

Example 3

1. Preparation of Microcapsules

Each electrophoretic dispersion, prepared in the same process as inExample 1, was added to 60 ml of an aqueous solution containing 4 g ofgelatin and 4 g of acacia gum, and the mixture was agitated at 800 rpmand encapsulated into capsules.

Thereafter, the untreated capsules were processed in a pH-adjusting stepusing acetic acid, sodium carbonate, etc., a cross-linking step usingformalin, a drying step, and the like in that order, wherebymicrocapsules corresponding to the individual colors were preparedrespectively.

2. Manufacturing of the Electrophoretic Display Device

First, a substrate having thin film transistor elements (TFT glasssubstrate) was obtained. The substrate was prepared by the same processas that for preparing TFT substrates used for manufacturing liquidcrystal displays.

The microcapsules of each of the colors (which are the same as inExample 4) had an average particle size of 50-60 μm, respectively.

Second, droplets containing an aqueous adhesive were each dischargedonto corresponding driving electrodes (separate electrodes),corresponding to red pixels, lying on the TFT glass substrate using anink-jet device (which was obtained by modifying a commercial ink-jetprinter).

Then, the red microcapsules were scattered (supplied) on the TFT glasssubstrate, followed by curing the adhesive thereby to fix themicrocapsules.

Subsequently, the same steps as the above ones were repeated to fix thegreen and blue microcapsules on the driving electrodes by the adhesivein turn.

Next, a glass substrate with an ITO layer on an entire surface thereofwas placed over the microcapsules. Then the substrates were gluedtogether with an emulsion binder (“PORON,” manufactured by Shin-EtsuChemical Co., Ltd.). Thus, an electrophoretic display device wasprepared.

When the terminal section of the resulting electrophoretic displaydevice was coupled with a power source through lines to try activatingthe device, the display device could be activated in multiple colorsincluding black, red, green, blue, and white. Also, the display devicecould be activated in a secondary color produced by these colors.

Example 4

The electrophoretic display device was manufactured by the same processas that of Example 3 except that microcapsules of four colors, preparedusing the electrophoretic dispersions prepared in the same process as inExample 2, were used.

As a result, an electrophoretic display device superior in display inblack to that in Example 3 could be obtained.

Example 5

The electrophoretic display device was manufactured by the same processas that of Example 2 except that acrylic particles (acrylic particleshaving hydroxyl groups), into which hydroxyl groups were introduced bycopolymerizing three parts of weight of acrylic monomers having hydroxylgroups with 100 parts of weight of the acrylic particles used in Example2, were used.

As a result, an electrophoretic display device superior in contrast tothe electrophoretic display device manufactured using unprocessedacrylic particles Example 2 could be obtained.

Example 6

The electrophoretic display device was manufactured by the same processas that of Example 4 except that acrylic particles having hydroxylgroups as in Example 5 were used.

As a result, an electrophoretic display device superior in contrast tothe electrophoretic display device manufactured using unprocessedacrylic particles Example 4 could be obtained.

Example 7

The electrophoretic display device was manufactured by the same processas that of Example 2 except that acrylic particles (acrylic particleshaving amino groups), into which amino groups were introduced bycopolymerizing three parts of weight of acrylic monomers having aminogroups with 100 parts of weight of the acrylic particles used in Example2, were used.

As a result, an electrophoretic display device superior in contrast tothe electrophoretic display device manufactured using unprocessedacrylic particles Example 2 could be obtained.

Example 8

The electrophoretic display device was manufactured by the same processas that of Example 4 except that acrylic particles having amino groupsas in Example 7 were used.

As a result, an electrophoretic display device superior in contrast tothe electrophoretic display device manufactured using unprocessedacrylic particles Example 4 could be obtained.

Example 9

Black microcapsules, prepared by the same process as that of Example 8,were mixed with an emulsion adhesive (“PORON,” manufactured by Shin-EtsuChemical Co., Ltd.), whereby microcapsule ink was prepared.

Then, the microcapsule ink was coated on a polyethylene terephthalatefilm having an ITO coating thereon and the resulting film was dried at90° C. for 10 minutes.

Subsequently, the substrate with microcapsules placed thereon was joinedwith the TFT element substrate. Thus, an electrophoretic display devicewas obtained.

When the terminal section of the resulting electrophoretic displaydevice was coupled with a power source through lines to try activatingthe device, the display device could be activated in monochrome, i.e. inblack and white. Also, the display device could be activated in asecondary color produced by these colors.

1. An electrophoretic dispersion, comprising: an insulative liquid phasedispersion medium; and electrophoretic particles dispersed in theinsulative liquid phase dispersion medium and electrophoreticallymigrated under an influence of an electric field; the electrophoreticparticles including inorganic particles and resin particles that aredyed a color different from a color of the inorganic particles and havean electrical polarity opposite to an electrical polarity of theinorganic particles.
 2. The electrophoretic dispersion according toclaim 1, the resin particles being composed mainly of an acrylic resin.3. The electrophoretic dispersion according to claim 2, the acrylicresin having at least one of a hydroxyl group or an amino group as apolar group.
 4. The electrophoretic dispersion according to claim 3, thepolar group being introduced by copolymerizing an acrylic monomer havingthe polar group with the acrylic resin.
 5. The electrophoreticdispersion according to claim 1, the resin particles being dyed any oneof red, green, blue, and black.
 6. The electrophoretic dispersionaccording to claim 1, the inorganic particles having an average particlesize of A[μm] and the resin particles having an average particle size ofB[μm], B/A falling in a range of 1.5-200.
 7. The electrophoreticdispersion according claim 1, the average particle size of the resinparticles being 0.5-20 μm.
 8. An electrophoretic display device,comprising: a first substrate; a second substrate opposed to the firstsubstrate; an electrophoretic dispersion located between the firstsubstrate and the second substrate; an insulative liquid phasedispersion medium included in the electrophoretic dispersion;electrophoretic particles dispersed in the insulative liquid phasedispersion medium and electrophoretically migrated under an influence ofan electric field; and a pair of electrodes to cause an electric fieldto act on the electrophoretic particles, the electrophoretic particlesincluding inorganic particles and resin particles that are dyed a colordifferent from a color of the inorganic particles and having anelectrical polarity opposite to an electrical polarity of the inorganicparticles.
 9. An electrophoretic display device, comprising: a firstsubstrate; a second substrate opposed to the first substrate;microcapsules located between the first substrate and the secondsubstrate; an electrophoretic dispersion encapsulated to themicrocapsules; an insulative liquid phase dispersion medium included inthe electrophoretic dispersion; electrophoretic particles dispersed inthe insulative liquid phase dispersion medium and electrophoreticallymigrated under an influence of an electric field; and a pair ofelectrodes to cause an electric field to act on the electrophoreticparticles, the electrophoretic particles including inorganic particlesand resin particles that are dyed a color different from the color ofthe inorganic particles and have an electrical polarity opposite to anelectrical polarity of the inorganic particles.
 10. The electrophoreticdisplay device according to claim 8, further comprising: a plurality ofthin film transistor elements arranged in a matrix and a plurality ofpixel electrodes that are one of the pair of electrodes, the thin filmtransistor elements corresponding to the pixel electrodes.
 11. Theelectrophoretic display device according to claim 8, further comprising:a plurality of thin film transistor elements arranged in a matrix; and aplurality of cell spaces partitioned off by partitions and formedbetween the first and second substrates, the cell spaces being eachfilled with the electrophoretic dispersion; and each of the cell spacescorresponding to at least one of the thin film transistor elements. 12.The electrophoretic display device according to claim 9, furthercomprising: a plurality of thin film transistor elements arranged in amatrix, plural kinds of the microcapsules including the resin particlesdyed different colors and being provided between the first and thesecond substrates, and each of the microcapsules corresponding to atleast one of the thin film transistor elements.
 13. A method ofmanufacturing the electrophoretic display device having a firstsubstrate, a second substrate opposed to the first substrate, anelectrophoretic dispersion located between the first substrate and thesecond substrate, an insulative liquid phase dispersion medium includedin the electrophoretic dispersion, electrophoretic particles dispersedin the insulative liquid phase dispersion medium and electrophoreticallymigrated under an influence of an electric field, a pair of electrodesto cause an electric field to act on the electrophoretic particles, anda plurality of thin film transistor elements arranged in a matrix andcorresponded to a plurality of pixel electrodes that are one of the pairof electrodes, comprising: forming a plurality of cell spaces betweenthe first substrate and the second substrate that are partitioned off bypartitions and that corresponded to at least one of the thin filmtransistor elements; and filling the cell spaces with a electrophoreticdispersion by a process using a dispenser or by an ink-jet method.
 14. Amethod of manufacturing the electrophoretic display device having afirst substrate, a second substrate opposed the first substrate, anelectrophoretic dispersion located between the first substrate and thesecond substrate, an insulative liquid phase dispersion medium includedin the electrophoretic dispersion, electrophoretic particles dispersedin the insulative liquid phase dispersion medium and electrophoreticallymigrated under an influence of an electric field, a pair of electrodesto cause an electric field to act on the electrophoretic particles, aplurality of thin film transistor elements arranged in a matrix andcorresponded to a plurality of pixel electrodes that are one of the pairof electrodes, and a plural kinds of microcapsules provided between thefirst substrate and the second substrate and corresponding to at leastone of the thin film transistor elements, comprising: fixing a givenkind of the microcapsules by an adhesive so as to be electricallyconnected with a target thin film transistor element of the thin filmtransistor elements, the given kind of the microcapsules including theresin particles dyed a given color and being fixed on the firstsubstrate or the second substrate; and repeating the fixing at least aplurality of times depending on the kind of microcapsules.
 15. Anelectronic system, comprising: the electrophoretic display deviceaccording to claim 8.